The present invention relates to a workpiece carrying apparatus. More particularly, the present invention relates to improvement in a shape or a material of an apparatus for taking out a workpiece such as liquid crystal glass from a cassette and carrying it to a predetermined position.
A workpiece carrying apparatus 101 for carrying a workpiece such as liquid crystal glass has, for example, a base 102, a first arm 103, a second arm 104 and a hand 105 as shown in FIG. 13. In this case, as a portion of the hand 105 for holding a workpiece (which will be simply referred to as a workpiece holding portion 105 hereinafter), a thin and elongated one which can carry a relatively large workpiece 106, enter a gap between the workpieces 106 piled up in the multilayer form at a narrow accommodation pitch and take out such a workpiece is preferable. Further, it is important that the workpiece holding portion 105 has the sufficient rigidity for reducing the deflection when holding the workpiece 106 and it is formed to be lightweight.
As such a workpiece holding portion 105, there is a flat bar obtained by, e.g., scraping off an aluminium material or carbon and molding it. As things stand now, as a material of the workpiece holding portion 105, aluminium or carbon mentioned above, stainless steel or ceramics is used to intend reduction in weight and provide the sufficient strength.
In recent years, however, with increase in size of the workpiece 106, the size of the workpiece holding portion 105 of the workpiece carrying apparatus 101 is also increased, and increase in weight of the workpiece holding portion 105 or the deflection involved by this increase becomes a problem. When the workpiece holding portion 105 is deflected in this manner, the workpiece 106 can not be safely and securely inserted or removed unless the accommodation pitch of the workpiece 106 in the cassette is increased. Furthermore, since the rectilinear movement property at the time of inserting or taking out the workpiece holding portion 105 is deteriorated because of the deflection, a moving velocity must be reduced, thereby prolonging the tact time required for carrying the workpiece 106. Moreover, the inertia also becomes large when the weight of the workpiece holding portion 105 is increased, and increasing an output for driving the workpiece holding portion 105 may result in enlargement of the dimension of the entire apparatus.
In addition, the workpiece holding portion 105 of the workpiece carrying apparatus 101 must have the structure for sucking the workpiece 106, i.e., a pad, a rubber material, a pipe, a sensor cable and others. It is required to accommodate these members while obtaining the thin shape as a whole. As such a thin workpiece holding portion 105, there is one having, e.g., a rectangular cross section. However, since such a workpiece holding portion 105 is formed by scraping off a solid-core material, the workpiece holding portion 105 itself has the solid-core structure. Thus, when the workpiece holding portion 105 is formed to be long in the longitudinal direction, the workpiece holding portion 105 may be deflected downwards by action of the uniformly distributed load by its own weight. In this case, a quantity of deflection becomes maximum at the end of the workpiece holding portion 105. Additionally, if its influence is considerable, the accuracy for inserting the workpiece holding portion 105 between the workpieces 106 is lowered.
It is, therefore, an object of the present invention is to provide a workpiece carrying apparatus which can be formed long while suppressing increase in weight of a workpiece holding portion for holding a workpiece, and which has the rigidity bearing off elongation. That is, it is an object of the present invention to form the workpiece holding portion as a long product which is lightweight and hardly deflected.
To achieve this aim, according to the present invention, there is provided a workpiece carrying apparatus comprising a hand for holding a workpiece and a moving mechanism for moving the hand in the horizontal direction, wherein a workpiece holding portion of the hand is formed by a horizontal holding arm which is extended in the horizontal direction and consists of a carbon fiber material, the horizontal holding arm has a horizontal arm portion opposed to a workpiece and at least one bent portion bent in a direction crossing the horizontal arm portion, and the surface of a corner portion on the border between the bent portion and the horizontal arm portion is rounded.
In this case, the horizontal holding arm is originally molded in shape such that a plate-like member is bent. As a result, a space is formed in a concave portion having a bent shape, and members required for sucking a workpiece are accommodated in this space. Therefore, the horizontal holding arm can be formed thin and compact as a whole while accommodating the respective members. Furthermore, when the plate-like member has the bent shape, the high flexural rigidity can be obtained. Moreover, in the present invention, since this horizontal holding arm is constituted by a carbon fiber material, the weight can be reduced and the high rigidity can be obtained. According to the present invention, the workpiece holding portion of the hand can be elongated while suppressing increase in weight, and the rigidity bearing off elongation is provided. Thus, a quantity of deflection when holding a workpiece is small, and a workpiece accommodated with a narrow pitch can be rapidly and assuredly carried.
In addition, since the surface of the bent portion on the workpiece side is rounded, interference hardly occurs even if the held workpiece is curved. Even if the workpiece is brought into contact with the bent portion, the surface of the workpiece is prevented from being damaged, and the static electricity is rarely generated to the liquid crystal glass as a workpiece.
According to the present invention, the horizontal holding arm is provided with the bent portions on both sides of the horizontal arm portion in the workpiece carrying apparatus, as described previously. In this case, the geometrical moment of inertia can be increased, and the flexural rigidity which is high for a cross sectional area can be obtained. When the horizontal arm portion is caused to be orthogonal to the bent portion in particular, the geometrical moment of inertia can be further increased.
Furthermore, when a space is formed on the back side of the horizontal arm portion and used so that the members and others required for suction can be accommodated in this space, a thin and compact workpiece holding portion can be formed.
According to the present invention, the horizontal holding arm is provided with a flange portion which is bent on the opposite side to the horizontal arm potion of the bent portion in the workpiece carrying apparatus as described above. In this case, the geometrical moment of inertia can be further increased, and the high flexural rigidity can be obtained. Moreover, since the flange portion is formed at least on one side of the horizontal holding arm, the geometrical moment of inertia can be further increased and the high flexural rigidity can be obtained.
According to the present invention, the flange portion is bent outward in the workpiece carrying apparatus described above. In this case, the horizontal holding arm has a crank-like or Z-shaped cross section formed by the horizontal arm portion, the bent portion and the flange portion, and the high geometrical moment of inertia can be obtained.
According tot he present Invention, the horizontal holding arm has a transverse cross section which is hollow elliptical. When the closed shape is used in this manner, the cross-sectional shape is hardly deformed, and a quantity of deflection at the end of the horizontal holding arm constituting the workpiece holding portion is small. Therefore, this is preferable as a large workpiece carrying apparatus in which the work holding portion is elongated.
According to the present invention, a suction portion for sucking a workpiece is caused to protrude on the front surface side of the horizontal arm portion and a holding mechanism for holding the suction portion and a pipe for suction are accommodated on the back surface side of the horizontal arm portion in the workpiece carrying apparatus as above. According to this apparatus, a workpiece can be carried while being sucked, and it is possible to form the thin work piece holding portion having the compact shape in which the holding mechanism and others are accommodated.
According to the present invention, the holding mechanism is accommodated in a space consisting of a concave portion formed between the horizontal arm portion and hte bent portion on the back surface side of the horizontal arm portion in the workpiece carrying apparatus as described above. When, e.g., taking out a workpiece, therefore, even if the workpiece is brought into contact with the back surface side of the horizontal holding arm, the surface of the workpiece can be prevented from being damaged by the holding mechanism.
According to the present invention, a workpiece is a laminated plate material, the horizontal arm portion includes a plurality of suction portions, and the laminated plate material is sucked and held by a plurality of the suction portions in the workpiece carrying apparatus as described above. Therefore, the plate material can be stably carried, and it is possible to cope with a plate material such as liquid crystal glass.